Steam Injection System and Method

ABSTRACT

An oven steam injection system includes an oven having a compartment enclosed on all sides, a door on a front side of the compartment, the door operable to open the compartment, and a steam injector disposed inside the compartment. The oven steam injection system also includes a steam generator having a heater reservoir and a heating element that is operable to heat water within the heater reservoir to generate steam. The steam generator is operable to inject steam into the compartment through the steam injector.

BACKGROUND

Disclosed herein is an oven steam injection system for heating food inan oven cavity, and particularly, a vehicle oven that directly injectssteam into the oven cavity.

Prior ovens for use in vehicles, such as aircraft, typically haveseveral elements disposed within the oven cavity and generate steamwithin the cavity. Such ovens typically include a heating element, aventilator, and a baffle plate to control an induced air flow inside theoven cavity. These additional elements in the oven cavity result in longheating times and typically require a high cavity temperature, whichalso results in a high external oven temperature.

SUMMARY

Various embodiments and related details of a novel vehicle oven arediscussed below.

According to an embodiment, an oven steam injection system includes anoven having a compartment enclosed on all sides, a door on a front sideof the compartment, the door operable to open the compartment, and asteam injector disposed inside the compartment. The system includes asteam generator having a heater reservoir and a heating element operableto heat water within the heater reservoir to generate steam, the steamgenerator operable to inject steam into the compartment through thesteam injector.

According to another embodiment, a method of injecting steam into anoven includes providing water in a heater reservoir that is disposedoutside of a compartment of the oven, heating the water in the heaterreservoir by a heating element to generate steam, and injecting steamfrom the heater reservoir into the compartment through a steam injectordisposed in the compartment.

While the exemplary embodiments described herein are presented in thecontext of an oven for an aircraft galley, these embodiments areexemplary only and are not to be considered limiting. The embodiments ofthe apparatus are not limited to ovens for use in an aircraft galley.For example, embodiments of the apparatus may be adapted for arefrigerator, freezer, and other food storage and cooking devices.Various embodiments may thus be used in any vehicle, including aircraft,spacecraft, ships, buses, trains, recreational vehicles, trucks,automobiles, and the like. Embodiments of the apparatus may also be usedin homes, offices, hotels, factories, warehouses, garages, and otherbuildings where it may be desirable to heat food with steam. In general,the embodiments may be used in any location or application in whichheating food with steam is desired.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are illustrated in the drawings and followingdiscussion:

FIG. 1A is a pictorial front view of an oven in an oven steam injectionsystem according to an embodiment, shown with an open door;

FIG. 1B is a pictorial front view of an oven in an oven steam injectionsystem according to another embodiment utilizing a fan and baffles,shown with an open door;

FIG. 2A is a schematic view of an oven steam injection system that usesheating elements below the oven cavity, according to an embodiment;

FIG. 2B is a schematic view of an oven steam injection system, accordingto another embodiment;

FIG. 2C is a schematic view of an oven steam injection system that usesa fan and baffles, according to another embodiment;

FIG. 2D is a schematic view of an oven steam injection system that usesheating elements below the oven cavity, according to another embodiment;

FIG. 2E is a schematic view of an oven steam injection system that usesheating elements below the oven cavity, according to another embodiment;

FIG. 3 is a top view of an arrangement of heating elements on the bottomof the oven cavity;

FIG. 4 is a flowchart of a method of controlling an oven steam injectionsystem, according to an embodiment; and

FIG. 5 is a flowchart of a method of controlling the amount of water inan oven steam injection system, according to an embodiment.

DETAILED DESCRIPTION

FIG. 1A is a front view of an oven with a door 13 in an open position toshow an oven cavity 1. The oven cavity 1 defines a confined space wheremeals are heated prior to consumption. Steam that is generated outsideof the oven cavity 1 is directly injected into the oven cavity 1 via oneor more holes 2 a of a steam injector 2 provided along a back wall 14 toheat the food provided therein.

There may be a single hole 2 a or a plurality of holes 2 a. AlthoughFIG. 1A shows a plurality of holes 2 a in a line, the holes could bearranged in a two-dimensional grid of any shape. The size, shape, andnumber of holes can be varied without departing from the spirit andscope of the invention.

Oven cavity 1 is provided with raisers 16 on a bottom 15 of the ovencavity 1 to aid in the draining of condensed water from oven cavity 1.The raisers 16 provide a place upon which oven contents, such as a tray,can rest and not be in contact with the floor 15 or water thataccumulates in the floor 15.

FIG. 1B is a front view of another embodiment having various otherfeatures. Instead of a plurality of holes 2 a, as is illustrated in FIG.1A, a single hole 2 a forms the mechanism by which steam is provided tothe cavity 1. To distribute the steam evenly, a fan 23 is located behindbaffles 22 that spread the steam out. Additional heaters 21, which maybe made of a positive temperature coefficient (PTC) material, orcomprise conventional resistor-type heating mechanisms, may be locatedoutside of the oven and attached to the bottom 15. FIG. 1B alsoillustrates a temperature sensor 19 that can be used to provideinformation back to a controller (described below). Any of theembodiments discussed herein may include such a temperature sensor 19.

FIG. 2A is a schematic of an embodiment of an oven steam injectionsystem S1. Steam is generated in a steam generator 3 having a heaterreservoir. Steam generated in the steam generator 3 is directly injectedinto the oven cavity 1 through the steam injector 2, which iscommunicatively coupled to the steam generator 3. The steam generator 3is located outside the oven cavity 1 and is dedicated to the preparationof steam. A heater element 4 contacts a bottom surface of the steamgenerator 3 and is operable to heat the steam generator 3 to convert thewater in the heater reservoir of steam generator 3 into steam.

Steam from the steam generator 3 is injected into the oven cavity 1,thereby heating the food in the oven cavity 1. As heat is transferred tothe food from the steam, the steam condenses into water, which is thencollected at a bottom 15 of the oven cavity 1, which may be recycled forsubsequent use. A cavity drain pump 6 is provided to pump the watercollected at the bottom 15 to a drain reservoir 7. The system 51 isfurther provided with a generator supply pump 5, which is operable topump water from the drain reservoir 7 to the heater reservoir in steamgenerator 3. Thus, the water condensed in oven cavity 1 is againgenerated into steam in the steam generator 3 and injected into the ovencavity 1 through steam injector 2.

Drain reservoir 7 is provided with a drain reservoir level sensor 12 fordetecting a level of water in the drain reservoir 7. When the level ofwater in the drain reservoir 7, as detected by the drain reservoir levelsensor 12, is below a predetermined low level drain threshold 7 a, anoven water supply valve 8 is opened to supply water to the drainreservoir 7 from a main water supply 10. The main water supply 10 could,for example, be an aircraft main water supply. Once the level of waterin the drain reservoir 7 detected by the drain reservoir level sensor 12is greater than the low level drain threshold 7 a (possibly by addingsome amount for hysteresis to limit the frequency with which the ovenwater supply valve 8 is opened/closed), the oven water supply valve 8 isclosed to stop the supply of water to the drain reservoir 7 from themain water supply 10.

The heater reservoir of the steam generator 3 is provided with agenerator level sensor 11 for detecting a level of water in the heaterreservoir of the steam generator 3. When the level of water in the steamgenerator 3, as detected by the generator level sensor 11, is below apredetermined low level heater threshold 3 a, the generator supply pump5 is operated to pump water from the drain reservoir 7 to the steamgenerator 3. Once the level of water in the steam generator 3 detectedby the generator level sensor 11 exceeds the low level heater threshold3 a (possibly by adding some amount for hysteresis to limit thefrequency with which the generator supply pump 5 isactivated/deactivated), the generator supply pump 5 is stopped to stopthe flow of water from the drain reservoir 7 to the steam generator 3.

When the level of water in the steam generator 3, as detected by thegenerator level sensor 11, is above a predetermined high level heaterthreshold 3 b, a generator drain valve 9 operatively coupled to thesteam generator 3 is opened to drain water from the steam generator 3 tothe drain reservoir 7. Once the level of water in the steam generator 3detected by the generator level sensor 11 is below the high level heaterthreshold 3 b (possibly by adding some amount for hysteresis to limitthe frequency with which the generator drain valve 9 is opened/closed),the generator drain valve 9 is closed to stop the draining of water fromthe steam generator 3.

When the level of water in the drain reservoir 7 is above a high leveldrain threshold 7 b and the level of water in the steam generator 3 isnot above the high level heater threshold 3 b, the generator supply pump5 is operated to pump water to the heater reservoir of steam generator3. In an optional embodiment, if the level of water in the drainreservoir 7 is above a high level drain threshold 7 b and the level ofwater in the steam generator 3 is also above the high level heaterthreshold 3 b (i.e., both reservoirs exceed respective high levelthresholds), an optional reserve drain valve 17 is opened to allow waterto go to the aircraft drain. Once the level of water in the drainreservoir 7 is below its high level drain threshold 7 b, the generatorsupply pump 5 can be stopped and the reserve drain valve 17 closed. Theoptional reserve drain valve 17 can also be present in any of theembodiments described herein. Any other mechanism for removing excesswater may also be provided.

The various functions described herein may be controlled by a controller20, which may be connected to any or all of the controllable and sensingelements described herein, including heater element 4, supply pump 5,cavity drain pump 6, water supply valve 8, generator drain valve 9,level sensors 11, 12, and drain valve 17.

In an embodiment, heaters 21 can be added to a side, such as the bottom15, of the oven cavity 1. These heaters can take on any form, but, in anembodiment, can be positive temperature coefficient (PTC) heaters thatare self-controlled and do not need an extra control system to avoidoverheating. This is because the natural resistance of the material usedfor the heaters will not allow the heaters to exceed some predeterminedtemperature. This heater 21 can be present in any of the embodimentsdisclosed herein. As discussed above, a hysteresis curve could be usedfor any of the high level and low-level values to more efficientlycontrol the process.

FIG. 2B is a schematic of another embodiment of an oven steam injectionsystem S2. According to the embodiment shown in FIG. 2B, the drainreservoir 7 is disposed below the oven cavity 1. The oven cavity 1 canbe extended to serve as a drain reservoir 7 (e.g., gravity fed), similarto a wet sump. Steam injected into the oven cavity 1 condenses and isfed into the drain reservoir 7 by gravity from the bottom 15 of the ovencavity 1. Condensed water from the drain reservoir 7 can then be pumpedto the steam generator 3 by the generator supply pump 5. Accordingly,the system S2 in FIG. 2B does not require the cavity drain pump 6 of thesystem S1 shown in FIG. 2A, although this design is more susceptible toissues related to aircraft orientations that differ from horizontal,which the FIG. 2A embodiment deals with more robustly. Alternatively,any mix of system components from system S1 and system S2 is alsopossible.

The injection of externally created steam into the oven cavity 1,according to embodiments, induces a large acceleration of air and steaminside the cavity, which provides the large condensation heat fluxnecessary for the rapid temperature rise of the meals being heated inthe oven cavity 1. The usage of externally supplied steam also providesfor a more uniform heating of the food within the oven cavity 1. Moreheat energy can be provided to the steam when it is externally created,since there are not the same size limitations for a heating unit to heatthe steam external to the cavity (and additionally, more of the space inthe oven cavity is available for food). Saturated steam injected intothe oven cavity 1 condenses on the coldest spots, thereby automaticallyreducing temperature differences. Thus, the temperature differencebetween meals heated in the oven cavity 1 is significantly reduced dueto the nature of the heating process. Further, for reasons of foodsafety, a minimum meal temperature is demanded when heated forconsumption. When temperature differences among the meals being heatedare large, more energy is required to meet this minimum meal temperaturerequirement because many meals will be heated to a higher temperature. Areduced temperature difference among meals in the oven cavity, asachieved by embodiments, will therefore save heating energy by reducingthe temperature the oven needs to reach to sufficiently heat each of themeals, and prevent the meals from being overcooked.

In addition, through the use of steam, the maximum internal temperatureof the oven cavity 1 can be reduced to, for example, just slightly abovethe condensation temperature of saturated steam, since internal heatingelements going significantly above this temperature to create the steamare not present. This reduces the outside temperature of the housing orcasing of the oven, thereby improving the safety of the oven to users.Additionally, because the internal temperature of the oven cavity 1 isreduced relative to prior ovens, less insulation material can beapplied. This results in weight savings that are particularly importantin aircraft oven systems and reduction in the cost of the oven system.

According to various embodiments, several structures that are generallyfound inside prior ovens are excluded from the oven cavity 1. Forexample, the oven cavity 1 does not need to include a ventilator, aheating element, and a baffle plate that controls the induced air flow,among others. Similarly, because steam is directly injected into theoven cavity 1, structures that were previously necessary to generatesteam within an oven cavity, such as a fan, are not necessary. In priorovens, these structures act as a parasitic thermal mass in the systemthat would need to be heated along with the food in the oven due totheir presence within the oven cavity. Because oven steam injectionsystems, according to various embodiments, eliminate the need forseveral structures internal to the oven cavity 1, the oven can have afaster response and heating relative to prior ovens, thereby improvingheating efficiency and energy savings.

According to embodiments, the water used to generate steam can berecycled, thereby providing additional weight savings. Prior systemsthat rely entirely upon a main water supply, such as an aircraft waterreserve, without recycling the condensed water in the oven cavity usemore of the water reserve than necessary. By recycling the condensedwater in the oven cavity, the use of the main water supply can bereduced, thereby saving weight by reducing the water reserve that isrequired.

Although the above considers systems in which there is no fan or baffle,there may be times when these features are desirable. FIG. 2Cillustrates such an embodiment that is similar to the embodiment shownin FIG. 2A, but that includes a baffle 22 and fan 23 with a fan motor24. In this embodiment, the steam injector 2 introduces the steam to theoven cavity 1 at a single point. In order, in this embodiment, to moreeffectively distribute the steam throughout the cavity 1, the fan blades23 rotate to move the steam from its introduction point 2 throughout thecavity 1. The baffle plate 22 allows the fan 23 to more effectively movethe steam to more distant parts of the cavity 1. Thus, a tradeoff ismade between the complexity of the steam introduction to the cavity 1and the inclusion of the baffle 22, fan 23, and its motor 24.

FIG. 2D is a schematic diagram illustrating a further embodiment. Thisembodiment includes the baffle 22, fan 23, and motor of the priorembodiment, but introduces the water 30 directly into the bottom 15 ofthe cavity 1 at a water input 31. The bottom has heater elements 21,such as the PTC elements 21 described above, affixed directly to a sideof the cavity 1 to have good thermal contact. Water is introduced viathe main water supply 10 with the oven water supply valve 8, andutilizes a flow meter 25 to correctly introduce the proper amount ofwater into the cavity 1, where the bottom portion of the cavity servesas a water reservoir (wet sump). Water exits the cavity 1 throughevaporation, although other draining mechanisms, as described above, canbe provided. The evaporated water can still, in this design, becondensed and further used. Stated differently, the heaters 21 can beused in any of the above-stated designs. These heaters 21 can be usedboth to generate steam in the cavity 1 as well as to dry out the cavity1 without running into an overheat situation. Two alternatives areprovided: in the first, water is gradually fed to the reservoir insidethe cavity in which the steam is generated. In the second, all waterrequired for the process is initially supplied (in an embodiment, thismight be, e.g., 700 cc).

FIG. 2E provides an embodiment that reduces water consumption and avoidsexcessive water vapor from being ejected into the galley and avoidscondensation on cold spots. In this embodiment, a pressure sensor 26monitors the cavity pressure, and the controller 20 is used to hold thepressure at very small over pressure to the air craft cabin pressure.The over pressure would typically be no more than 20 mbar. The ovenstarts with an air valve 32 open. At first, total air pressure builds updue to the rise of the partial pressure of the injected water vapor(steam). This mix of air and water vapor is vented through the valve 32air opening. Once the temperature sensor 19 indicates a temperature thatcorresponds with the saturated vapor pressure at cabin pressure(typically 94° C.) the air valve 32 is closed.

From this point on, the cavity is closed and over pressure is maintainedby regulating the heating power. Typically, approximately 200 cc ofwater is accumulated on the meal carrier and the meals (however, thisvaries with each type of oven and contents). The cavity walls and floormay accumulate 100 cc of water, and, at cabin pressure the amount ofwater vapor that is in the cavity volume is approximately 30 g. Intotal, roughly 350 cc of water is evaporated and accumulated in theoven. Advantageously, the cavity over-pressure controlled power controlcan anticipate cabin pressure variations and the control system is notdependent on ambient pressure of the oven. Cavity over-pressurecontrolled power has the potential to save water. Alternatively, thecavity temperature could be monitored and used to control the heatingpower.

FIG. 3 is an example layout of the bottom 15 to which bottom heaters 21have been affixed.

FIG. 4 is a flowchart illustrating a process of controlling an ovensteam injection system, according to an embodiment. The process ofcontrolling the system can be implemented by the controller 20 having aprocessor communicatively coupled with a memory. The process begins atstep 400 where a user initiates the desired heating of food within ovencavity 1. For example, the heating process may be based on apredetermined amount of heating time or based on reaching a desired foodtemperature. At step 401, the water level in drain reservoir 7 isdetected by drain reservoir level sensor 12 and compared with apredetermined low level threshold 7 a at step 402. If the level of waterin the drain reservoir 7 is below the low level threshold 7 a, theprocess proceeds to step 403. At step 403, water is added to the drainreservoir 7 from the main water supply 10, and the level of water isdetected again.

If the level of water in drain reservoir 7 is not below the low levelthreshold 7 a at step 402, the process proceeds to step 404 where thelevel of water in the heater reservoir of steam generator 3 is detectedby the generator level sensor 11. If the level of water in the heaterreservoir 3 c is below a low level threshold 3 a, the process proceedsto step 406 where water is pumped to the heater reservoir 3 c from drainreservoir 7 by operating generator supply pump 5. The process thenreturns to steps 404 and 405 where the level of water in the heaterreservoir 3 c is detected and compared to the low threshold 3 a.

If the level of water in the heater reservoir 3 c is not below the lowthreshold 3 a at step 405, the process proceeds to step 407. At step407, the water in the heater reservoir 3 c is heated by the heatingelement 4 to generate steam within the steam generator 3. At step 408,the steam generated in steam generator 3 is injected into the ovencavity 1 through the steam injector 2. As the steam condenses within theoven cavity 1, water is collected at the bottom 15 of the oven cavity atstep 409. The condensed water is then transferred to drain reservoir 7at step 410. In the embodiment depicted in FIG. 2A, the cavity drainpump 6 pumps the collected water to the drain reservoir 7. In theembodiment depicted in FIG. 2B, water is collected in drain reservoir 7by the force of gravity on the condensed water.

At step 411, the system determines whether heating has concluded. Forexample, if the heating process is based on a predetermined heatingtime, a timer may be included for tracking the time of the process. Oncethe elapsed time tracked by the timer reaches the predetermined heatingtime, the process terminates at step 412. If the elapsed time has notyet reached the predetermined heating time, the process proceeds to step401 where the process is repeated. Alternatively, for example, theheating process may be based upon reaching a desired food temperature. Atemperature sensor 19 for detecting the food temperature within the ovencavity 1, and transmitting the food temperature to a controller in thesystem, may be provided. This temperature sensor can either monitor airtemperature within the oven cavity 1, or can measure the temperature ofthe food directly, such as via a probe or via an infra-red sensorreading.

When the food temperature detected by the temperature sensor reaches thepredetermined desired food temperature, the process terminates at step412. If the food temperature has not yet reached the desired foodtemperature, the process proceeds to step 401 where the process isrepeated. The processor may determine a proper amount of steam to sendto the food based on a measured temperature and knowledge of a desiredtemperature, and may also use a time history of the warming temperatureto adapt to the thermal mass being heated. Based on thesedeterminations, it can determine how much steam to deliver to ensure acorrect temperature is reached. When the condensing pressure has reachedcabin pressure, the power should be controlled in order to avoid excessevaporation that will only escape into the cabin.

FIG. 5 is a flowchart illustrating a process for controlling the waterin an oven steam injection system, according to an embodiment. Inparticular, FIG. 5 depicts steps that may occur between steps 401 and404 shown in FIG. 4. When the level of water in the drain reservoir 7detected by the drain reservoir level sensor 12 exceeds the low leveldrain threshold 7 a (NO at step 402), in an optional procedure, thelevel of water in the drain reservoir 7 is compared with a high leveldrain threshold 7 b at step 501. If the level of water in the drainreservoir 7 is determined to exceed the high level drain threshold (YESat step 501), the level of water in the heater reservoir is 3 c detectedat step 502 and compared with a high level heater threshold 3 b at step503.

If the level of water in the heater reservoir exceeds the high levelheater threshold 3 b (YES at step 503), i.e., the levels of water inboth reservoirs 3 c, 7 exceed respective high level thresholds 3 b, 7 b,the reserve drain 17 is opened at step 505 to allow water to return tothe main water supply 10 from the drain reservoir 7. The process thenreturns to step 401. If the level in heater reservoir 3 c does notexceed the high level heater threshold 3 b (NO at step 503), thegenerator supply pump 5 is operated to pump water from the drainreservoir 7 to the heater reservoir 3 c at step 504. The process thenreturns to step 401. Once the level of water in the drain reservoir 7 isbelow its high level threshold 7 b (NO at step 501), the generatorsupply pump 5 can be stopped and the reserve drain valve 17 closed, ifnecessary, at step 506. The process then continues with step 404 andsubsequent steps as described above.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

For the purposes of promoting an understanding of the principles of theinvention, reference has been made to the embodiments illustrated in thedrawings, and specific language has been used to describe theseembodiments. However, no limitation of the scope of the invention isintended by this specific language, and the invention should beconstrued to encompass all embodiments that would normally occur to oneof ordinary skill in the art. The terminology used herein is for thepurpose of describing the particular embodiments and is not intended tobe limiting of exemplary embodiments of the invention. In thedescription of the embodiments, certain detailed explanations of relatedart are omitted when it is deemed that they may unnecessarily obscurethe essence of the invention.

The use of any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. Numerous modifications and adaptations will bereadily apparent to those of ordinary skill in this art withoutdeparting from the spirit and scope of the invention as defined by thefollowing claims. Therefore, the scope of the invention is defined notby the detailed description of the invention but by the followingclaims, and all differences within the scope will be construed as beingincluded in the invention.

No item or component is essential to the practice of the inventionunless the element is specifically described as “essential” or“critical”. It will also be recognized that the terms “comprises,”“comprising,” “includes,” “including,” “has,” and “having,” as usedherein, are specifically intended to be read as open-ended terms of art.The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless the context clearly indicates otherwise. In addition, itshould be understood that although the terms “first,” “second,” etc. maybe used herein to describe various elements, these elements should notbe limited by these terms, which are only used to distinguish oneelement from another. Furthermore, recitation of ranges of values hereinare merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein.

TABLE OF REFERENCE CHARACTERS

S1-S5 system embodiments1 oven cavity2 steam injector2 a steam injector hole3 steam generator3 a low level heater threshold3 b high level heater threshold3 c heater reservoir4 heater element5 generator supply pump6 cavity drain pump7 drain reservoir7 a drain reservoir low level threshold7 b drain reservoir high level threshold8 oven water supply valve9 generator drain valve10 main water supply11 generator level sensor12 reservoir level sensor14 rear wall15 bottom16 raisers17 drain valve19 temperature sensor21 bottom heaters, PTC heater22 baffle plate23 fan24 motor25 flow meter26 pressure sensor30 water31 water input32 air valve400-505 method steps

What is claimed is:
 1. An oven steam injection system comprising: anoven comprising: a compartment enclosed on all sides; a door on a frontside of the compartment, the door operable to open the compartment; anda steam injector disposed inside the compartment; and a steam generatorexternal to the compartment, comprising: a heater reservoir; and aheating element operable to heat water within the heater reservoir togenerate steam, the steam generator operable to inject steam into thecompartment through the steam injector.
 2. The oven steam injectionsystem of claim 1, further comprising: a drain disposed at a bottom ofthe compartment, the drain operable to collect water from condensedsteam at the bottom of the compartment; and a drain pump operable topump the water collected in the drain to the heater reservoir.
 3. Theoven steam injection system of claim 2, further comprising: a drainreservoir; a generator supply pump; and a generator level sensor fordetecting a level of water in the heater reservoir, wherein: the drainpump is operable to pump the water collected in the drain to the drainreservoir; and the generator supply pump is operable to pump water fromthe drain reservoir to the heater reservoir when the level of water inthe heater reservoir as detected by the generator level sensor is belowa predetermined low heater reservoir threshold.
 4. The oven steaminjection system of claim 3, further comprising: a water supplyoperatively connected to the drain reservoir; and a drain reservoirlevel sensor for detecting a level of water in the drain reservoir,wherein the water supply provides water to the drain reservoir when thelevel of water in the drain reservoir as detected by the drain reservoirlevel sensor is below a predetermined low drain reservoir threshold. 5.The oven steam injection system of claim 1, further comprising: a drainreservoir disposed below the compartment, the drain reservoir operableto collect water by gravity from steam that has condensed in thecompartment; a generator supply pump; and a generator level sensor fordetecting a level of water in the heater reservoir, wherein thegenerator supply pump is operable to pump water from the drain reservoirto the heater reservoir when the level of water in the heater reservoiras detected by the generator level sensor is below a predetermined lowheater reservoir threshold.
 6. The oven steam injection system of claim5, further comprising: a water supply operatively connected to the drainreservoir; and a drain reservoir level sensor for detecting a level ofwater in the drain reservoir, wherein the water supply provides water tothe drain reservoir when the level of water in the drain reservoir asdetected by the drain reservoir level sensor is below a predeterminedlow drain reservoir threshold.
 7. The oven steam injection system ofclaim 1, further comprising: compartment heating elements that arelocated on a side of the compartment.
 8. The oven steam injection systemof claim 7, wherein the compartment heating elements are PTC elements.9. The oven steam injection system of claim 1, further comprising: afan; a motor that drives the fan; and a baffle plate located in front ofthe fan; wherein the fan, motor, and baffle plate are configured toevenly distribute the injected steam throughout the compartment.
 10. Theoven steam injection system of claim 9, wherein the steam injectorinjects steam at a single point within the compartment.
 11. A method ofinjecting steam into an oven, the method comprising: providing water ina heater reservoir that is disposed outside of a compartment of theoven; heating the water in the heater reservoir by a heating element togenerate steam; injecting steam from the heater reservoir into thecompartment through a steam injector disposed in the compartment. 12.The method of claim 11, further comprising: collecting water fromcondensed steam in a drain at a bottom of the compartment; pumping thewater collected in the drain to the heater reservoir.
 13. The method ofclaim 12, further comprising: detecting a level of water in the heaterreservoir; pumping the water collected in the drain to a drain reservoirby a drain pump; and then pumping water from the drain reservoir to theheater reservoir by a generator supply pump when the level of water inthe heater reservoir is below a predetermined low heater reservoirthreshold.
 14. The method of claim 13, further comprising: detecting alevel of water in the drain reservoir; and supplying water to the drainreservoir by a water supply when the level of water in the drainreservoir is below a predetermined low drain reservoir threshold. 15.The method of claim 11, further comprising: collecting water in a drainreservoir disposed below the compartment, the water being collected inthe drain reservoir by gravity from steam that has condensed in thecompartment; detecting a level of water in the heater reservoir; andpumping water from the drain reservoir to the heater reservoir by agenerator supply pump when the level of water in the heater reservoir isbelow a predetermined low heater reservoir threshold.
 16. The method ofclaim 15, further comprising: detecting a level of water in the drainreservoir; and supplying water to the drain reservoir by a water supplywhen the level of water in the drain reservoir is below a predeterminedlow drain reservoir threshold.
 17. An steam oven system comprising: anoven comprising: a compartment enclosed on all sides; a door on a frontside of the compartment, the door operable to open the compartment; anda water input disposed inside the compartment; and a heating elementexternal to the compartment; and a water supply valve that controls anamount of water entering the compartment at the water input; wherein:water that enters the compartment via the water input and that contactsa surface of the compartment is heated by the heating element togenerate steam within the compartment.
 18. The steam oven of claim 17,further comprising: a fan; a motor that drives the fan; and a baffleplate located in front of the fan; wherein the fan, motor, and baffleplate are configured to evenly distribute the injected steam throughoutthe compartment.
 19. The steam oven of claim 17, further comprising aflow control element that introduces water at a predetermined rate whilethe heating elements are operating.
 20. The steam oven of claim 17,further comprising a flow control element that introduces apredetermined volume of water prior to operating the heating elements.21. The steam oven of claim 17, further comprising: a pressure sensor;and a controller that maintains a minimal pressure difference betweenthe compartment and ambient pressure by manipulating energy provided tothe heating elements.
 22. The steam oven of claim 21, furthercomprising: an air vent through which steam and water can be vented toaddress a pressure buildup.
 23. The steam oven of claim 21, furthercomprising: a temperature sensor; and a controller that maintains apredefined temperature by manipulating energy provided to the heatingelements.